A little appreciated fact is that the internal forces generated in cams placed in downward-flaring placements can be arbitrarily high. See, for example, Vaino Kodas's explanation. Among other things, he says, "...as the angle of the flare approaches the spiral angle the forces grow very large (theoretically infinite)..."

What this means in practical terms is that cams in flaring placements are susceptible to forces that will break either the placement or the cam (or both). I'd guess that usually the placement breaks in some way and the cam is extracted by the fall, but breakage is another possible failure mode. This is a consequence of the camming geometry and is not a design failure.

This is one of the key posts in this thread. Anyone who has been reading this thread and who hasn't already clicked through to the Kodas paper, ought to do so. For those too lazy, his conclusion on cams in flares reads as follows:

"A little experimentation shows that as the angle of the flare approaches the spiral angle (tan-1µ) the forces grow very large (theoretically infinite). There will be a large compression force on the cams, a large shear force on the axle, and a large spreading force on the walls of the crack. Most likely, at these high forces, significant bending and/or deformation would take place so that the above equations would no longer be valid."

In other words, forces on cams in flared placements are much higher than in parallel-sided placements, and we ought to expect "deformation." One could reasonably expect "material failure" in even a normal cam in such a placement given a high-load fall. In a fall in which the cam was leveraged, which was clearly the case in this instance, forces would be higher and more complicated.

The Kodas finding is significant because its predictions proved out in the informal testing that Malcolm has described in which a variety of brand name cams, in off-plumb placements, failed in ways that includedwhat we've all been rather vaguely referring to as "material failure." Or rather, the inference that Malcolm, Richard, Michael and other knowlegeable folks are making is that the placement begins to shift or fail and then weird forces multiply and stuff starts to break.

I find it difficult to imagine a generalizable lab situation-- i.e., one that could become an industry standard test --that could really usefully replicate the wild variety of flare/angle/lean/leverage situations we find the the big wide world.

We've all probably taken at least a few falls onto weird cam placements that we knew to be sub-standard, but to judge from what I read on this site, the collective willingness of folks in the community to take those sort of risks has actually increased. Or maybe the ability to recognize those risks has diminished. Or both. My guess is that as more and more climbers are willing to regularly lob onto cams in weird flared placements, we are going to see more and more "exploding cams," and not just those of the "my-tweakeremployee-forgot-to-braze-it" variety.

A little appreciated fact is that the internal forces generated in cams placed in downward-flaring placements can be arbitrarily high. See, for example, Vaino Kodas's explanation. Among other things, he says, "...as the angle of the flare approaches the spiral angle the forces grow very large (theoretically infinite)..."

What this means in practical terms is that cams in flaring placements are susceptible to forces that will break either the placement or the cam (or both). I'd guess that usually the placement breaks in some way and the cam is extracted by the fall, but breakage is another possible failure mode. This is a consequence of the camming geometry and is not a design failure.

This is one of the key posts in this thread. Anyone who has been reading this thread and who hasn't already clicked through to the Kodas paper, ought to do so. For those too lazy, his conclusion on cams in flares reads as follows:

"A little experimentation shows that as the angle of the flare approaches the spiral angle (tan-1µ) the forces grow very large (theoretically infinite). There will be a large compression force on the cams, a large shear force on the axle, and a large spreading force on the walls of the crack. Most likely, at these high forces, significant bending and/or deformation would take place so that the above equations would no longer be valid."

In other words, forces on cams in flared placements are much higher than in parallel-sided placements, and we ought to expect "deformation." One could reasonably expect "material failure" in even a normal cam in such a placement given a high-load fall. In a fall in which the cam was leveraged, which was clearly the case in this instance, forces would be higher and more complicated.

The Kodas finding is significant because its predictions proved out in the informal testing that Malcolm has described in which a variety of brand name cams, in off-plumb placements, failed in ways that includedwhat we've all been rather vaguely referring to as "material failure." Or rather, the inference that Malcolm, Richard, Michael and other knowlegeable folks are making is that the placement begins to shift or fail and then weird forces multiply and stuff starts to break.

I find it difficult to imagine a generalizable lab situation-- i.e., one that could become an industry standard test --that could really usefully replicate the wild variety of flare/angle/lean/leverage situations we find the the big wide world.

We've all probably taken at least a few falls onto weird cam placements that we knew to be sub-standard, but to judge from what I read on this site, the collective willingness of folks in the community to take those sort of risks has actually increased. Or maybe the ability to recognize those risks has diminished. Or both. My guess is that as more and more climbers are willing to regularly lob onto cams in weird flared placements, we are going to see more and more "exploding cams," and not just those of the "my-tweakeremployee-forgot-to-braze-it" variety.

Yes. What Vaino is saying is that placing a cam in a flare has exactly the same effect as employing a cam with a very small cam angle--i.e. at the extreme the useful range of the cam goes to zero and the outward force goes to infinity. This concept is fairly well known among those who actually understand how these things work, although it may not be all that intuitive to everyone.

edited to add:

So, you can see that in extremely flared placements, the deck is pretty much stacked against you. The cam has a very small expansion range and the outward forces are high enough to likely either deform the cam or fracture the rock itself.

Here is a picture of a Cassin Joss cam that broke in a short fall that resulted in a fatality in the Gunks. The relevant post is here. It is possible that the accident may have been the result of an overly brittle construction, but of course in order to break a cam that isn't defective a lot of force is required, regardless of the alloy in question. My guess is that this was another case of the effect of flaring placements, perhaps additionally complicated by pebbly nubbins that could have restricted the cams ability to pivot, although remember that this was a horizontal placement.

Cams are complicated devices whose security cannot be evaluated in the same way as a nut---consider, for example, the Metolius tests that suggested that one in twenty "well-placed" cams fail. Essentially, cams are faith-based protection, the faith in question being with the engineering principles that are supposed to be in effect. The fact that those same principles can engender arbitrarily large forces seems to be conveniently ignored---for example, no one paid the slightest attention to my post in this thread on that subject until k.l.k. resurrected it.

As for gear-makers responsibility to ensure that the (nearly blind) faith we would like to place in their gear is justified, it is important to remember that climbing gear cannot be engineered to withstand industrial safety margins and still be carried up the hill. The nature of the endeavor forces engineering decisions that could prove catastrophic in the field, and climbers need to understand that. I am not trying to excuse shoddy quality control, but simply say that fond as we may be of the concept of bombproof gear; it isn't, never was, and never will be.

Climbers' faith in cams has certainly been justified over the years by many successful performances, but on the other hand cams do fail on occasion in spite of being judged good. The fact that they don't break more often may simply be a reflection that the rock will usually give way first. It seems plausible that the link cam stayed in and broke while most other cams would have pulled out. If this is true, then what you have in all cases is a cam failure. Psychologically, people are far more likely to accept an extraction as part of the game than breakage, even if the breakage occurs, paradoxically, because of extra holding power.

I don't know whether any of these assertions are true in the case at hand, but they are certainly true in general: the ability of cams to hold and not break is dependent on a host of conditions, only some of which are realistically under a climber's control. Any time a cam is placed suboptimally, the chances of failure go up, and honestly, we really have no idea how much.

I think what is beginning to emerge from all this is a sense that cams are not at all the "no-brainer" protection they may have seemed to be at first, and perhaps a broad change of attitude is called for. People used to say that nuts required all kinds of thought and ingenuity and with cams you just fired in a unit. But cams are mechanically far more complicated and less predictable than nuts, and perhaps it is time to emphasize the respect and consideration their complexity demands.

In both this case and the terribly sad Gunks tragedy, the cam that broke could have been backed up, in the case of the Gunks tragedy with good nuts. When faith-based protection leads us to skip readily available options for redundancy, I think it is time to rethink the entire approach.

Well spoken as always Rgold. If anyone is feeling that this effect is counterintuitive, I suppose a similar feel you could get would be to put your arms straight out in a chimney. When they are out at 30degrees, not too hard to hold your weight- but as they go out further, the pressure increases dramatically.

It make sense to me: thank you to all the calm, intelligent people who have posted and contributed to the information flow and discussion.

I just learned something I need (and you need) to know.

Thanks!

Some of the rest of you should seriously consider your words and effect on others.

I will say, that younger climbers seem able to pitch off with wild abandon and trust in places where old timers refuse to fall (or go if they think they will fall). Applying sport tactics to regular gear placements is increasing in usage and has been discussed on various RC.com and other forums extensively: it is a tactic for experts. Unfortunately, as soon as a young person gets out of the gym (where dogging is derigeur, common and safe), they do not see a difference where one actually exists in a huge way.

Not to say this example was one of those, but it's a side issue to accompany this knowledge and rgolds point.

What can ya do? (Edited to get rid of that "some of you other assholes can lick my sweaty asscrack" comment as it was mean spirited, aggro, pointless and non-productive)

Some of the rest of you should seriously consider your words and effect on others.

Bill asked me a question in this thread and followed up to ask me in a PM as well...

'do you still use CCH Aliens' to which I responded to as .... 'mostly retired' but yes I do still use them from time to time.

He expressed surprise that I could still use Aliens despite their track record and at the same time 'slam' Link cams for this failure.

I wasn't taken abck by the charge of 'slamming them' because I knew my post was provocative when I typed it.

However, if you think about it....well hell, with one line edited I will simply post my PM back to Bill for all to read, I think there is pertinence:

Dingus to Bill PM wrote:

Hi Bill

Thanks for the note. To clarify one thing, I did not slam the Links. I spoke frankly of 'market fears.' What I wrote is what OP needs to hear, imo.

I wasn't that I was dissatisified in any way with the OP quick response and open analysis process. On the contrary, I am impressed, esp. when compared to CCH.

I have a long track historyt of open and vocal support of OP and their products as well, dating back ten plus years.

I also wrote the Link review here on rc.com as you may know. One of the caveats I listed in that article was that the jury was still out in terms of durability.

Well the jury is STILL out, but now the word on the street is its 9-3 voting to convict (lack of durability).

The conclusion of the OP analysis is the same as mine, only reworded. Michael said as a direct result of this failure they are going to not only create more test jigs for unusual placement and fall angles, they were also going to reevaluate the design and construction as well.

Dude I can read between the lines the same as others....

So here we have a cam at 30 degrees to the angle of fall, unable to rotate, failing completely. OK.... it begs the questions....

what about 25 degrees? Ten?

What if the cam is nearly in line but still unable to rotate? One or two or 5 degrees?

Maybe other cams would have failed in the same spot, maybe not. I doubt many of them would explode frankly. I would expect cam deformation, for example, on any decent sized metolious or black diamond cam. I suspect many would pull out rather than exploding. Perhaps the Link held TOO WELL in this case quien sabe?

My main point here is I don't know, you don't know and most importantly, OP doesn't know.

We can all chat about the garage-mechanic-engineer days of yesteryear all we wish. In a production world of CE certs and UIAA standards, shit has got to work as advertised. This notion that 'climbing gear fails and you're a fool for thinking a cam could not explode' is total bullshit.

Cheers Bill DMT

I also tire at the Brilliant After-the-Fact Analysts here who 'knew it all along.' Bunch more bullshit right there.

Thanks Dingus: I think one of the points I made was: this was a single failure, and people seem to be using and hucking on them without any issues to date. Compare and contrast to Aliens, which are an irregular pattern of poorly made and tested cams.

Getting an answer vis a vis Rich Goldstones great post above was basically what I was looking for. That the placement was bad. That a Metolius or a BD may have broken, or just pull out of that placement, ie, still fail, by rock being destroyed.

Cassin cam failure above Rich linked which resulted in a fatality in a similar fall.

That makes much more sense then buying a cam that doesn't break. And motorcycles and kayaks aren't designed to save you.

In reply to:

I haven't bought any yet, but I'm damn sure going to buy some now, if for no other reason just to help Michael and OP offset a little of the costs they incurred to investigate this incident and report the results to the climbing community.

Jay, you can't sell it or give it away for free because you are a failed pathetic excuse for a software developer.

In reply to:

With you on the board, I should be selling the Killfile, rather than giving it away for free.

I'm not a software developer at all -- never have even claimed to be. In fact, quite the opposite, as I have said before, my original reason for writing the killfile script was to teach myself Javascript. Nonetheless, the scripts I've written for this website have been downloaded 634 times to date.

I'm constantly amazed at how stupid people are so willing to make public fools of themselves by making unjustified assumptions that are so easily shown to be false.

Jay, you can't sell it or give it away for free because you are a failed pathetic excuse for a software developer.

In reply to:

With you on the board, I should be selling the Killfile, rather than giving it away for free.

There's a couple of things you could have done better here, pay attention.

1. You went personal early, now if the argument escalates you've got nothing left in the hopper but "I fucked your mother/sister/dad/dog/grandma". Weaksauce. Next time save the nitro for the finish line.

2. You picked the wrong topic. Here you've opted to ignore the macro-topic for the site (climbing) and have decided to talk shit about Jay's professional status, or lack thereof. This is a problem because nobody actually believes you have any fucking clue what Jay's professional status might look like. For the record I am a decidedly unpathetic and relatively well-paid excuse for an application developer and I'll tell you right now that if Jay where to put in a job app I'd probably hire him, assuming he knows CSS and can get around in a unix command line.

3. You picked the wrong thread. You've just hijacked an accident report that includes product beta from the manufacturer. This is about as serious as a thread gets on here. Folks weren't following this thread breathlessly waiting for your next fucktard post. If you want to be a fucktard and get away with it, better to start a new thread.